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MILLER/SPOOLMAN
LIVING IN THE ENVIRONMENT
17TH
Chapter 5
Biodiversity, Species
Interactions, and Population
Control
Core Case Study: Southern Sea Otters: Are
They Back from the Brink of Extinction?
• Habitat
• Hunted: early 1900s
• Partial recovery
• Why care about sea otters?
• Ethics
• Tourism dollars
• Keystone species
Southern Sea Otter
Figure 5.1: An endangered southern sea otter in Monterey Bay, California (USA), uses a stone to crack
the shell of a clam (left). It lives in a giant kelp bed (right). Scientific studies indicate that the otters act as
a keystone species in a kelp forest system by helping to control the populations of sea urchins and other
kelp-eating species.
Fig. 5-1a, p. 104
5-1 How Do Species Interact?
• Concept 5-1 Five types of species interactions—
competition, predation, parasitism, mutualism, and
commensalism—affect the resource use and
population sizes of the species in an ecosystem.
Species Interact in Five Major Ways
• Interspecific Competition
• Predation
• Parasitism
• Mutualism
• Commensalism
Most Species Compete with One
Another for Certain Resources
• For limited resources
• Ecological niche for exploiting resources
• Some niches overlap
Some Species Evolve Ways to Share
Resources
• Resource partitioning
• Using only parts of resource
• Using at different times
• Using in different ways
Resource Partitioning Among Warblers
Figure 5.2: Sharing the wealth: This diagram illustrates resource partitioning among five species of
insect-eating warblers in the spruce forests of the U.S. state of Maine. Each species minimizes
competition with the others for food by spending at least half its feeding time in a distinct portion
(yellow highlighted areas) of the spruce trees, and by consuming somewhat different insect species.
(After R. H. MacArthur, “Population Ecology of Some Warblers in Northeastern Coniferous Forests,”
Ecology 36 (1958): 533–536.)
Fig. 5-2, p. 106
Specialist Species of Honeycreepers
Figure 5.3: Specialist
species of honeycreepers:
Through natural selection,
different species of
honeycreepers developed
specialized ecological
niches that reduced
competition between
these species. Each
species has evolved a
specialized beak to take
advantage of certain
types of food resources.
Fig. 5-3, p. 107
Most Consumer Species Feed on Live
Organisms of Other Species (1)
• Predators may capture prey by
1. Walking
2. Swimming
3. Flying
4. Pursuit and ambush
5. Camouflage
6. Chemical warfare
Predator-Prey Relationships
Fig. 5-4, p. 107
Most Consumer Species Feed on Live
Organisms of Other Species (2)
• Prey may avoid capture by
1. Run, swim, fly
2. Protection: shells, bark, thorns
3. Camouflage
4. Chemical warfare
5. Warning coloration
6. Mimicry
7. Deceptive looks
8. Deceptive behavior
Some Ways Prey Species Avoid
Their Predators
Figure 5.5: These prey species
have developed specialized
ways to avoid their predators:
(a, b) camouflage, (c–e)
chemical warfare, (d, e)
warning coloration, (f) mimicry,
(g) deceptive looks, and (h)
deceptive behavior.
Fig. 5-5, p. 109
camouflage
(a) Span worm
Fig. 5-5a, p. 109
camouflage
(b) Wandering leaf insect
Fig. 5-5b, p. 109
chemical
warfare
(c) Bombardier beetle
Fig. 5-5c, p. 109
chemical
warfare
(d) Foul-tasting monarch butterfly
Fig. 5-5d, p. 109
warning
coloration
(e) Poison dart frog
Fig. 5-5e, p. 109
warning
coloration
(f) Viceroy butterfly mimics monarch
butterfly
Fig. 5-5f, p. 109
mimicry
(g) Hind wings of Io moth resemble
eyes of a much larger animal.
Fig. 5-5g, p. 109
mimicry
(h) When touched, snake
caterpillar changes shape to look
like head of snake.
Fig. 5-5h, p. 109
(a) Span worm
(c) Bombardier beetle
(e) Poison dart frog
(g) Hind wings of Io moth
resemble eyes of a much
larger animal.
(b) Wandering leaf insect
(d) Foul-tasting monarch butterfly
(f) Viceroy butterfly mimics
monarch butterfly
(h) When touched,
snake caterpillar changes
shape to look like head of snake.
Stepped Art
Fig. 5-5, p. 109
Science Focus: Threats to Kelp Forests
• Kelp forests: biologically diverse marine habitat
• Major threats to kelp forests
1. Sea urchins
2. Pollution from water run-off
3. Global warming
Purple Sea Urchin
Fig. 5-A, p. 108
Predator and Prey Interactions Can
Drive Each Other’s Evolution
• Intense natural selection pressures between
predator and prey populations
• Coevolution
• Interact over a long period of time
• Bats and moths: echolocation of bats and sensitive
hearing of moths
Coevolution: A Langohrfledermaus
Bat Hunting a Moth
Fig. 5-6, p. 110
Some Species Feed off Other Species
by Living on or in Them
• Parasitism
• Parasite is usually much smaller than the host
• Parasite rarely kills the host
• Parasite-host interaction may lead to coevolution
Parasitism: Trout with Blood-Sucking Sea Lamprey
Fig. 5-7, p. 110
In Some Interactions, Both Species
Benefit
• Mutualism
• Nutrition and protection relationship
• Gut inhabitant mutualism
• Not cooperation: it’s mutual exploitation
Mutualism: Hummingbird and Flower
Figure 5.8:
Mutualism: This
hummingbird
benefits by feeding
on nectar in this
flower, and it
benefits the flower
by pollinating it.
Fig. 5-8, p. 110
Mutualism: Oxpeckers Clean Rhinoceros; Anemones
Protect and Feed Clownfish
Figure 5.9: Examples of mutualism: (a) Oxpeckers (or tickbirds) feed on parasitic ticks
that infest large, thick-skinned animals such as the endangered black rhinoceros. (b) A
clownfish gains protection and food by living among deadly, stinging sea anemones and
helps to protect the anemones from some of their predators.
Fig. 5-9, p. 111
In Some Interactions, One Species Benefits
and the Other Is Not Harmed
• Commensalism
• Epiphytes
• Birds nesting in trees
5-2 What Limits the Growth of
Populations?
• Concept 5-2 No population can continue to grow
indefinitely because of limitations on resources and
because of competition among species for those
resources.
Most Populations Live Together in
Clumps or Patches (1)
• Population: group of interbreeding individuals of the
same species
• Population distribution
1. Clumping
2. Uniform dispersion
3. Random dispersion
Most Populations Live Together in
Clumps or Patches (2)
• Why clumping?
1. Species tend to cluster where resources are
available
2. Groups have a better chance of finding clumped
resources
3. Protects some animals from predators
4. Packs allow some to get prey
Population of Snow Geese
Fig. 5-11, p. 112
Generalized Dispersion Patterns
Figure 5.12: This diagram illustrates three general dispersion patterns for
populations. Clumps (a) are the most common dispersion pattern, mostly
because resources such as grass and water are usually found in patches.
Where such resources are scarce, uniform dispersion (b) is more common.
Where they are plentiful, a random dispersion (c) is more likely. Question:
Why do you think elephants live in clumps or groups?
Fig. 5-12, p. 112
Populations Can Grow, Shrink, or
Remain Stable (1)
• Population size governed by
•
•
•
•
Births
Deaths
Immigration
Emigration
• Population change =
(births + immigration) – (deaths + emigration)
Populations Can Grow, Shrink, or
Remain Stable (2)
• Age structure
• Pre-reproductive age
• Reproductive age
• Post-reproductive age
Some Factors Can Limit Population
Size
• Range of tolerance
• Variations in physical and chemical environment
• Limiting factor principle
• Too much or too little of any physical or chemical
factor can limit or prevent growth of a population,
even if all other factors are at or near the optimal
range of tolerance
• Precipitation
• Nutrients
• Sunlight, etc
Trout Tolerance of Temperature
Figure 5.13: This diagram illustrates the range of tolerance for a population of organisms, such as trout, to
a physical environmental factor—in this case, water temperature. Range of tolerance restrictions prevent
particular species from taking over an ecosystem by keeping their population size in check. Question: For
humans, what is an example of a range of tolerance for a physical environmental factor?
Fig. 5-13, p. 113
No Population Can Grow Indefinitely:
J-Curves and S-Curves (1)
• Size of populations controlled by limiting factors:
•
•
•
•
•
Light
Water
Space
Nutrients
Exposure to too many competitors, predators or
infectious diseases
No Population Can Grow Indefinitely:
J-Curves and S-Curves (2)
• Environmental resistance
• All factors that act to limit the growth of a population
• Carrying capacity (K)
• Maximum population a given habitat can sustain
No Population Can Grow Indefinitely:
J-Curves and S-Curves (3)
• Exponential growth
• Starts slowly, then accelerates to carrying capacity
when meets environmental resistance
• Logistic growth
• Decreased population growth rate as population size
reaches carrying capacity
Logistic Growth of Sheep in Tasmania
Figure 5.15: This graph
tracks the logistic growth of
a sheep population on the
island of Tasmania between
1800 and 1925. After sheep
were introduced in 1800,
their population grew
exponentially, thanks to an
ample food supply and few
predators. By 1855, they had
overshot the land’s carrying
capacity. Their numbers then
stabilized and fluctuated
around a carrying capacity of
about 1.6 million sheep.
Fig. 5-15, p. 115
Science Focus: Why Do California’s Sea
Otters Face an Uncertain Future?
• Low biotic potential
• Prey for orcas
• Cat parasites
• Thorny-headed worms
• Toxic algae blooms
• PCBs and other toxins
• Oil spills
Population Size of Southern Sea Otters Off the Coast of
So. California (U.S.)
Figure 5.B: This graph tracks the population size of southern sea otters off the coast of the U.S. state of
California, 1983–2009. According to the U.S. Geological Survey, the California southern sea otter population
would have to reach at least 3,090 animals for 3 years in a row before it could be considered for removal from
the endangered species list. (Data from U.S. Geological Survey)
Fig. 5-B, p. 114
Case Study: Exploding White-Tailed
Deer Population in the U.S.
• 1900: deer habitat destruction and uncontrolled hunting
• 1920s–1930s: laws to protect the deer
• Current population explosion for deer
• Spread Lyme disease
• Deer-vehicle accidents
• Eating garden plants and shrubs
• Ways to control the deer population
Mature Male White-Tailed Deer
Fig. 5-16, p. 115
When a Population Exceeds Its Habitat’s
Carrying Capacity, Its Population Can Crash
• A population exceeds the area’s carrying capacity
• Reproductive time lag may lead to overshoot
• Population crash
• Damage may reduce area’s carrying capacity
Exponential Growth, Overshoot, and
Population Crash of a Reindeer
Figure 5.17: This graph tracks
the exponential growth,
overshoot, and population
crash of reindeer introduced
onto the small Bering Sea
island of St. Paul. When 26
reindeer (24 of them female)
were introduced in 1910,
lichens, mosses, and other
food sources were plentiful. By
1935, the herd size had soared
to 2,000, overshooting the
island’s carrying capacity. This
led to a population crash,
when the herd size plummeted
to only 8 reindeer by 1950.
Question: Why do you think
the sizes of some populations
level off while others such as
the reindeer in this example
exceed their carrying
capacities and crash?
Fig. 5-17, p. 116
Species Have Different Reproductive
Patterns (1)
• Some species
•
•
•
•
Many, usually small, offspring
Little or no parental care
Massive deaths of offspring
Insects, bacteria, algae
Species Have Different Reproductive
Patterns (2)
• Other species
•
•
•
•
•
•
•
Reproduce later in life
Small number of offspring with long life spans
Young offspring grow inside mother
Long time to maturity
Protected by parents, and potentially groups
Humans
Elephants
Under Some Circumstances Population
Density Affects Population Size
• Density-dependent population controls
•
•
•
•
Predation
Parasitism
Infectious disease
Competition for resources
Several Different Types of Population
Change Occur in Nature
• Stable
• Irruptive
• Population surge, followed by crash
• Cyclic fluctuations, boom-and-bust cycles
• Top-down population regulation
• Bottom-up population regulation
• Irregular
Population Cycles for the Snowshoe Hare and
Canada Lynx
Figure 5.18: This graph represents the population cycles for the snowshoe hare and the Canadian lynx.
At one time, scientists believed these curves provided evidence that these predator and prey
populations regulated one another. More recent research suggests that the periodic swings in the hare
population are caused by a combination of top-down population control—through predation by lynx
and other predators—and bottom-up population control, in which changes in the availability of the food
supply for hares help to determine their population size, which in turn helps to determine the lynx
population size. (Data from D. A. MacLulich)
Fig. 5-18, p. 118
Humans Are Not Exempt from
Nature’s Population Controls
• Ireland
• Potato crop in 1845
• Bubonic plague
• Fourteenth century
• AIDS
• Global epidemic
5-3 How Do Communities and Ecosystems
Respond to Changing Environmental
Conditions?
• Concept 5-3 The structure and species composition
of communities and ecosystems change in response
to changing environmental conditions through a
process called ecological succession.
Communities and Ecosystems Change over
Time: Ecological Succession
• Natural ecological restoration
• Primary succession
• Secondary succession
Some Ecosystems Start from Scratch:
Primary Succession
• No soil in a terrestrial system
• No bottom sediment in an aquatic system
• Takes hundreds to thousands of years
• Need to build up soils/sediments to provide
necessary nutrients
Primary Ecological Succession
Figure 5.19: Primary ecological succession: Over almost a thousand years, these plant communities
developed, starting on bare rock exposed by a retreating glacier on Isle Royal, Michigan (USA) in northern
Lake Superior. The details of this process vary from one site to another. Question: What are two ways in
which lichens, mosses, and plants might get started growing on bare rock?
Fig. 5-19, p. 119
Some Ecosystems Do Not Have to Start from
Scratch: Secondary Succession (1)
• Some soil remains in a terrestrial system
• Some bottom sediment remains in an aquatic system
• Ecosystem has been
• Disturbed
• Removed
• Destroyed
Natural Ecological Restoration of Disturbed Land
Figure 5.20: Natural ecological restoration of disturbed land: This diagram shows the undisturbed secondary ecological succession of plant
communities on an abandoned farm field in the U.S. state of North Carolina. It took 150–200 years after the farmland was abandoned for the
area to become covered with a mature oak and hickory forest. A new disturbance such as deforestation or fire would create conditions favoring
pioneer species such as annual weeds. In the absence of new disturbances, secondary succession would recur over time, but not necessarily in
the same sequence shown here. See an animation based on this figure at CengageNOW. Questions: Do you think the annual weeds (left) would
continue to thrive in the mature forest (right)? Why or why not?
Fig. 5-20, p. 120
Secondary Ecological Succession in Yellowstone Following
the 1998 Fire
Figure 5.21: These young lodgepole pines growing around standing dead trees after a
1998 forest fire in Yellowstone National Park are an example of secondary ecological
succession.
Fig. 5-21, p. 120
Some Ecosystems Do Not Have to Start from
Scratch: Secondary Succession (2)
• Primary and secondary succession
• Tend to increase biodiversity
• Increase species richness and interactions among species
• Primary and secondary succession can be interrupted by
•
•
•
•
•
Fires
Hurricanes
Clear-cutting of forests
Plowing of grasslands
Invasion by nonnative species
Science Focus: How Do Species Replace One
Another in Ecological Succession?
• Facilitation
• Inhibition
• Tolerance
Succession Doesn’t Follow a
Predictable Path
• Traditional view
• Balance of nature and a climax community
• Current view
• Ever-changing mosaic of patches of vegetation
• Mature late-successional ecosystems
• State of continual disturbance and change
Living Systems Are Sustained through
Constant Change
• Inertia, persistence
• Ability of a living system to survive moderate
disturbances
• Resilience
• Ability of a living system to be restored through
secondary succession after a moderate disturbance
• Some systems have one property, but not the other:
tropical rainforests
Three Big Ideas
1. Certain interactions among species affect their use
of resources and their population sizes.
2. There are always limits to population growth in
nature.
3. Changes in environmental conditions cause
communities and ecosystems to gradually alter
their species composition and population sizes
(ecological succession).